Internal combustion engines improvements continue to aim to increase energy efficiency, so that a smaller part of the chemical energy contained in the fuel is converted into thermal energy. One drawback to this strategy may include poorer warming behavior of the internal combustion engine after a cold start.
A cold internal combustion engine may lead to a higher fuel consumption because of increased internal engine friction and sub-optimal combustion process. In addition, the issue of condensation water may occur in the case of an external low-pressure exhaust gas recirculation device assigned to the internal combustion engine. Because the temperature falls below the dew point, an undesirable condensation can form, in particular in the low-pressure cooler for the low-pressure exhaust gas for recirculation (low-pressure EGR cooler) and in the low-pressure valve which controls the output of exhaust gas for recirculation to the intake air tract of the internal combustion engine (low-pressure EGR valve).
Here, firstly so-called free flow condensate may form when water contained in the warm or hot and damp recirculated low-pressure exhaust gas condenses when cooling on contact with cold fresh air. Initially small droplets agglomerate into larger droplets. If these larger droplets hit a rapidly rotating impeller, they may degrade (e.g., crack) blades thereof.
Secondly, so-called wall condensation occurs wherein the warm or hot recirculated low-pressure exhaust gas meets a cold wall, whereby the recirculated exhaust gas cools together with the water contained therein. If, for a given proportion of gaseous water, cooling occurs to a temperature below the dew point for this water proportion, condensation may result.
The condensation water occurring may enter the intake air tract of the internal combustion engine together with the recirculated low-pressure exhaust gas. If the condensate hits the impeller of the turbocharger, the condensation droplets can cause erosion of the compressor vanes since, because of their mass, they constitute an obstacle to the vanes at the compressor rotation speeds occurring. This wear has negative effects on the efficiency of the compressor, the fuel consumption, the emission of pollutants and the development of vibrations (NVH: noise, vibration, harshness). In addition, the condensation water may cause misfiring in petrol engines.
Therefore, it may be desired to reduce or eliminate the occurrence of condensation water upstream of the compressor.
One example approach to decrease condensate formation in the LP-EGR passage and/or LP-EGR cooler is shown by Hebert et al. in DE 102017202128. Therein, an exhaust heat recovery system comprises a first heat exchanger and a refrigerant circuit with coolant flowing therethrough. The exhaust heat recovery system may decrease condensate formation in parts of the LP-EGR system, such as the LP-EGR cooler. However, the exhaust heat recovery system fails to heat the EGR valve during an engine cold-start, which may still receive a considerable amount of condensate formation.
Another example approach is shown by Styles et al. in U.S. Pat. No. 8,960,166. Therein, coolant in a pre-compressor duct wall may be used to decrease condensate formation on a pre-compressor duct. The heated engine coolant may also pass through the EGR valve body. However, this coolant flow needs significant manufacturing and is not easily introduced onto current road-going vehicles.
The inventors have identified the above problems and come up with a way to at least partially solve them. In one example, the issues are addressed by a system, comprising a tempering circuit for flowing a tempering medium from a container to an engine cooling circuit, an EGR cooler, and an EGR valve. In this way, a cold-start duration of the engine may be reduced as may a likelihood of condensate formation in the EGR cooler and on the EGR valve.
As one example, the tempering circuit may be fitted with a plurality of control valves shaped to adjust tempering medium flow to various portions of the tempering circuit. By doing this, tempering medium flow to the EGR valve and the EGR cooler may be adjusted such that one or more other may be heated while the other is not. This may provide more rapid heating of one EGR component, which may further mitigate condensate formation.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.